Rationale
Presently, our students are exposed to a lot of information through media, television and other electronic gadgets. Statistical numbers are presented to them daily. For example in science, students are informed that global warming has affected the population of the polar bears. The population of the Eurasian Lynx is below fifty thousand. There are approximately 100 pairs of Bearded Vultures left. The Amur leopard has a population of 40 individuals. It is important to teach the students estimation strategies because it will help them understand the magnitude of small and large numbers. They will be able to take a guess with common sense when they fully grasp the concept. Thus, estimated numbers will be meaningful to them, and they should use the skills learned as often as possible in their everyday life to maintain them.
Students must understand that estimation is beyond guesswork. Estimation is an important skill because it helps students make sense of what is around them. Carlow (1986) describes estimation skills as making intuitive judgments within a holistic framework. Taylor - Cox (2001) called this the range-based estimation. The rationale for finding a range of numbers rather one definitive number is based on the belief that if an exact answer is required then individuals should be doing something other than estimating, e.g., mental math maybe more appropriate. According to Taylor-Cox estimation should be used when it is not important to find an exact answer, or it is too difficult to calculate one quickly.
Some people believe that the person who could estimate to the closest number is the best estimator. Research explains that when adults and children were asked to provide estimate in the inquiry, the adults estimated to the closest number while the children provided the researcher with wild guesses. Leutzinger, Rathmell and Urbatsh explain for that for a young child, there is little difference between 35 and 1000; they are both large numbers (Leutzinger et al 1986.p82)
Children should be taught the estimation process clearly so that as the children mature their mathematical thinking matures and develop a clear understanding of estimation. Thus, estimation has to be taught in a continuum. For example, the students in third grade begin to round off numbers to the nearest 10 and 100 to approximate reasonable results in problem situations. When the students move up to fourth grade they are expected to round whole numbers to the nearest 10, 100, and 1000 to approximate reasonable results in problem situations. In fifth grade, the students are using strategies to round and finding compatible numbers to estimate solutions to addition, subtraction, multiplication and division problems.
Carlow (1986) used the term "perceptual anchor", e.g. what might 10, 20, or 100 look like. Siegel, Goldsmith and Madson (1982) used the term "benchmarks" to describe nonstandard units, such as, "How many glasses of water are there in a bucket?" Perceptual anchor, referent, or benchmark refers to the number of chunks in a whole. Reys, Suydam, Lindquist and Smith (1998) refer to the refinement of chunking as unitizing.
I mentioned above that children should learn estimation in their early childhood years. One concrete example of estimation activities that can be taught to the children is putting 30 jelly beans in a jar. I will work with them to find out how about how many jelly beans are there in a whole jar. I will record their different estimated numbers. As a whole class, we will remove the jelly beans from the jar and put them in arrays to find out the total number. After that, we will compare the numbers found with their responses. Allow the students to explain their answer choices.
Another example of an activity to show the range of numbers is the number line. Give the students any four numbers within the range of 11-20. Let them use sticky notes to find the numbers in the number line. When the students can visualize that a gummy worm is the size of their finger, then strategies of using referents will help them understand the concept of estimation and lead them to be better thinkers. Every year students make progress in their estimation skills. The estimation problems become more complex in terms of quantities and analysis.
Comments: